The present invention relates in general to air conditioning systems and particularly to a central air conditioning system arranged with local re-conditioning units. More particularly, the present invention is concerned with a combination of such a local air conditioning unit and an illuminating appliance for installation on a ceiling structure of a relatively large-sized building.
While the central air conditioning system incorporating the improvement according to the present invention may be useful for the comfort cooling and heating of residential buildings and premises or for district air conditioning purposes, the same will prove advantageous particularly when installed in relatively large-sized, multiroom and/or multistory structures such as business, commercial, industrial, institutional or public buildings as will be understood as the description proceeds.
The capabilities, performance characteristics and dimensional details of a single-duct central air conditioning system are usually determined in the process of planning and designing the building in which the air conditioning system is to be installed. When the building is completed and transferred to the client or to tenants of the client from the contractor, it is usual that the users of the building have the floors or the existing compartments of each of the floors partitioned into sections and subsections depending upon the purposes for which the floor spaces are to be utilized. This results in change in the distribution of conditioning air supplied from the central conditioning unit and circulated through the spaces in the floors. The draughts of air into the spaces to be conditioned therefore vary from one section or subsection to another and, in the worst case, there will be such sections or subsections that are not directly ventilated from the distribution ductwork of the air conditioning system and are thus not or, at most, only poorly air conditioned. Such localized distribution of conditioning air also results from the sensible loads located in the space or spaces to be air conditioned, such as heat-emanating or heat-absorbing equipment and appliances, illumination for the space or spaces, and gains or losses of heat due to solar and sky radiation through the envelope of the building such as the roof structure, exterior walls, window panes and other kinds of skins.
To remedy the localized distribution of the conditioning air, it has been an ordinary practice to have the air distribution ductwork of the conditioning system locally re-arranged so as to compensate for the change in the load. This will compel the owner or the tenants of the building to incur extra expenses. Because, moreover, the ductwork is re-arranged only locally for the purpose of saving the cost and because of the fact that the central air conditioning unit per se is usually not re-adjusted or exchanged, the initially designed balance in the operation of the system tends to be destroyed even after the ductwork is re-arranged and, as a consequence, there will still exist sections or subsections which are only poorly air conditioned or the capacity of the system per se will become short of meeting the total demand of the building. For the purpose of providing a solution to these problems inherent in the central air conditioning system of the single-duct design, it has been proposed to have the central air conditioning system arranged with supplementary local air re-conditioning units so that the conditioning air is "zoned" to the individual spaces to be air conditioned. The local re-conditioning units are mounted within ceiling chambers of the building, using the chambers as part of the air distribution ductwork. A problem however arises in mounting the local re-conditioning units within the ceiling chambers because it frequently happens that the areas optimum for locating the re-conditioning units have been occupied or designed to be occupied by illuminating appliances for the rooms to be air conditioned and limit the range of selection of the locations available for the installation of the re-conditioning units. The performance of the local re-conditioning units must therefore be sacrificed if priority is given to the illuminating appliances. Ceiling or attic mounted air conditioners per se are well known in the art from, for example, U.S. Pat. Nos. 2,682,757, 2,770,955, 2,817,217 and 3,625,022. None of the prior art air conditioners taught in these issued patents aims at providing a solution to the problems above pointed out. The air conditioner disclosed in each of the patents uses outdoor air as a source of heat or as a medium to be heated by the rejected heat and basically differs in principle of operation from the local air re-conditioning unit combined with the central air conditioning system in that the re-conditioning unit is operative to exchange heat with the air which has once been heated or cooled by the central air conditioning system and which has been circulated through the space or spaces to be air conditioned.
The present invention contemplates elumination of the above described problems encountered in the prior art air re-conditioning units which are used supplementarily to the central air conditioning system of, typically, the single-duct design.